Method of Controlling Automated Guided Vehicle, Automated Guided Vehicle and System

The instant application claims priority to International Patent Application No. PCT/EP2023/075021, filed Sep. 15, 2023, which is incorporated herein in its entirety by reference.

The present disclosure generally relates to automated guided vehicles (AGVs) and, more particularly, to a method of controlling an AGV, an AGV, and a system comprising an AGV.

Automated guided vehicles, AGVs, are typically self-powered, self-driven vehicles. AGVs may be used to transport materials and other items from one location to another, without the need for a driver on the vehicle. An AGV may also comprise a manipulator for performing various tasks. AGVs are commonly used in manufacturing sites, warehouses, post offices, libraries, port terminals, airports, and some hazardous locations and specialty industries.

WO 2020259830 A1 discloses a method of braking an AGV. The AGV comprises a support structure and at least three drive units connected to the support structure. The method comprises positioning wheels of the drive units in an invalid configuration, and position controlling each wheel about a respective steering axis in the invalid configuration. Although the method in WO 2020259830 A1 provides a good universal solution for braking the AGV, the invalid wheel configuration is not adapted to any specific loads.

If an AGV comprising a manipulator is instructed to be at standstill while performing a task using the manipulator, there is a risk that the task fails if a support structure of the AGV moves (e.g., translationally moves and/or rotates) even slightly. In order to account for such risk, the manipulator may only carry out relatively simple low accuracy tasks and at low speeds, frequent recalibrations of the AGV may be required, and/or interactions between the manipulator and its environment, such as pushing operations, may be avoided. All these measures limit the productivity of the AGV. The manipulator may also be prevented from performing more complicated tasks when the stability of the support structure is not ensured. The use of dedicated brakes to hold the support structure at standstill significantly increases the cost of the AGV.

The present disclosure generally describes an improved method of controlling an automated guided vehicle (AGV), an improved AGV, and/or an improved system. In one general aspect, by representing an application load on an AGV by a remote force acting at a remote point, and by orienting wheels of the AGV such that an instant center of rotation, ICR, thereof coincides with the remote point, an increased stiffness of the AGV can be obtained.

According to a first aspect, there is provided a method of controlling an automated guided vehicle, AGV, the AGV comprising a support structure and at least three wheel units, each wheel unit comprising a wheel rotatable around a horizontal wheel axis; wherein for at least two of the wheel units, the wheel unit comprises a steering motor arranged to drive the wheel around a vertical steering axis; and wherein the method comprises providing a support point in relation to the support structure; providing an application load in relation to the support structure, the application load comprising an application force; representing the application load by a remote force acting at a remote point horizontally offset from the support point, and acting in a horizontal remote direction transverse to an offset line between the support point and the remote point; and for the at least two of the wheel units comprising a steering motor, positioning each wheel in a steering position such that an instant center of rotation, ICR, of each wheel substantially coincides with, or coincides with, the remote point.

In the following, a method of controlling an automated guided vehicle, AGV, an AGV and a system comprising an AGV, will be described. The same or similar reference numerals will be used to denote the same or similar structural features.

1 FIG. 1 FIG. 1 FIG. 10 10 12 10 12 14 16 12 a a a. schematically represents a side view of a system. The systemcomprises an automated guided vehicle, AGV. The systemmay thus be referred to as an AGV system. In, the AGVis positioned on a horizontal ground surface, here exemplified as a floor.further shows a human usernext to the AGV

12 18 12 20 18 20 22 22 18 14 12 20 a a a a a a a a 1 FIG. The AGVcomprises a support structure, here exemplified as a platform. The AGVof this example further comprises four wheel units(only two are visible in) connected to the support structure. Each wheel unitcomprises a wheel. Each wheelis arranged to support the support structureon the ground surface. The AGVmay further comprise a power source (not shown), such as a battery, to power the wheel units.

1 FIG. 24 1 24 2 24 1 18 24 2 14 further shows a local coordinate system-and a global coordinate system-. In this example, the local coordinate system-is fixed with respect to the support structureand the global coordinate system-is fixed with respect to the ground surface.

12 26 26 18 18 a The AGVof this example further comprises a manipulator, here exemplified as a serial robot arm programmable in at least three axes. The manipulatoris supported on the support structureand is movable relative to the support structure.

26 28 30 28 32 32 18 The manipulatorof this example comprises plurality of joints, a plurality of actuatorsfor driving respective joints, and a plurality of links, including a first link. The first linkis rotatable relative to the support structurearound a vertical axis as shown with a corresponding arrow.

12 34 12 34 36 38 38 36 36 38 12 12 12 14 26 18 18 a a a a a The AGVfurther comprises an electronic control systemconfigured to control the AGV. The control systemof this example comprises a data processing deviceand a memory. The memoryhas a computer program stored therein. The computer program comprises program code which, when executed by the data processing device, causes the data processing deviceto perform, or command performance of, various steps as described herein. An AGV control program is also stored in the memory. When the AGV control program is executed, the AGVis controlled to perform various tasks. The AGV control program may comprise movement instructions for the AGV. The movement instructions may comprise instructions which, when executed, causes the AGVto move over the ground surface, and movement instructions which, when executed, causes the manipulatorto move relative to the support structureto perform a task while the support structuremoves and/or is at standstill.

26 40 42 40 28 42 28 40 42 34 26 40 28 42 28 34 26 40 42 The manipulatorof this example further comprises one or more torque sensorsand one or more force sensors. Each torque sensoris arranged to sense a torque at an associated jointand each force sensoris arranged to sense a force at an associated joint. Each torque sensorand each force sensoris in signal communication with the control system. According to one example, the manipulatorcomprises a torque sensorat each jointand one force sensor, e.g., at a most distal joint. In any case, the control systemmay be configured to determine any force or torque acting on the manipulatorbased on signals from the one or more torque sensorsand the one or more force sensors.

40 42 26 26 26 40 42 The one or more torque sensorsand the one or more force sensorsare however optional. For each trajectory of the manipulatordefined in the AGV control program, the resulting forces and torques can also be calculated at one or more arbitrarily chosen points of the manipulatorwithout necessarily executing the trajectory by the manipulatorand without using the one or more torque sensorsand the one or more force sensors. The skilled person is aware of such calculations. In this regard, reference can for example be made to WO 2022171283 A1, the content of which is incorporated in its entirety herein by reference.

10 44 16 44 44 34 The systemof this example further comprises a programming device, here exemplified as a teach pendant unit, TPU. The usermay create and/or modify the AGV control program using the programming device. In this example, the programming deviceis configured to wirelessly communicate with the control system.

2 FIG. 2 FIG. 20 12 12 12 20 a a a a a schematically represents a cross-sectional view of one specific example of a wheel unitfor the AGV. The AGVis only partially illustrated in. The AGVof this specific and non-limiting example comprises four wheel unitsof the same design.

20 46 22 48 48 46 22 50 48 50 48 50 48 50 48 20 50 20 a a a a a a a a a a a a a a a a. 2 FIG. The wheel unitof this specific and non-limiting example comprises a driven steering member. The wheelis rotatable around a wheel axisto generate a tractive force in a heading direction transverse to the wheel axis. The driven steering memberand the wheelare rotatable around a steering axis. The wheel axisis perpendicular to the steering axis. Moreover, the wheel axisintersects the steering axis. In, the wheel axisis horizontal and the steering axisis vertical. The wheel axisprovides a first degree of freedom for the wheel unit. The steering axisprovides a second degree of freedom for the wheel unit

20 52 52 22 48 52 22 52 22 a a a a a. The wheel unitfurther comprises a drive motor, here exemplified as an electric synchronous drive motor. The drive motoris arranged to rotationally drive the wheelaround the wheel axis. In this example, the drive motoris arranged to directly drive the wheel, i.e. without any intermediate gearing between the drive motorand the wheel

20 54 54 46 50 54 52 22 12 20 20 12 18 a a a a a a a The wheel unitfurther comprises a steering motor, here exemplified as an electric synchronous steering motor. The steering motoris arranged to rotationally drive the driven steering memberaround the steering axis. The steering motorand the drive motormay for example each provide a torque of at least 5 Nm. The wheelof this example is thus a steerable and drivable wheel. Since the AGVof this example comprises at least two wheel units, here four wheel units, the AGVcan perform an omnidirectional motion of the support structure.

54 46 54 46 46 56 58 56 2 FIG. The steering motoris arranged to directly drive the driven steering member, i.e. without any intermediate gearing between the steering motorand the driven steering member. The driven steering memberof the example incomprises a support structure partand two arm partsextending downwards from the support structure part.

20 60 62 46 50 60 18 12 54 64 66 68 66 56 68 64 56 66 a a a The wheel unitfurther comprises a steering shaftand two steering bearingsfor rotationally supporting the driven steering memberaround the steering axis. The steering shaftis rigidly connected to the support structureof the AGV. The steering motorcomprises a steering stator, a steering rotorand steering coils. The steering rotoris arranged inside the support structure part. The steering coilsare arranged on the steering stator. In this example, the support structure partis an integral part of the steering rotor.

20 70 70 46 22 50 70 34 70 72 74 a a a The wheel unitfurther comprises a steering sensor device. The steering sensor devicedetermines a rotational position of the driven steering member, and consequently also of the wheel, around the steering axis. The steering sensor deviceis in signal communication with the control system. The steering sensor deviceof this example comprises an active part, here constituted by a Hall effect steering sensor, and a passive part, here constituted by a multipole steering encoder ring.

20 76 72 76 74 46 a The wheel unitfurther comprises a steering circuit board. The Hall effect steering sensoris provided on the steering circuit board. The steering encoder ringis connected to the driven steering member.

52 78 80 82 78 22 82 78 20 84 86 22 48 84 58 46 a a a a The drive motorcomprises a wheel stator, a wheel rotorand wheel coils. The wheel statoris arranged inside the wheel. The wheel coilsare arranged on the wheel stator. The wheel unitfurther comprises a wheel shaftand two wheel bearingsfor rotationally supporting the wheelaround the wheel axis. The wheel shaftis rigidly connected to the arm partsof the driven steering member.

20 88 88 70 88 22 48 88 34 88 90 92 a a a The wheel unitfurther comprises a wheel sensor device. The wheel sensor devicemay be of the same type as the steering sensor device. The wheel sensor devicedetermines a rotational position of the wheelaround the wheel axis. The wheel sensor deviceis in signal communication with the control system. The wheel sensor deviceof this example comprises an active part, here constituted by a Hall effect wheel sensor, and a passive part, here constituted by a multipole wheel encoder ring.

20 94 90 94 92 22 a a. The wheel unitfurther comprises a wheel circuit board. The Hall effect wheel sensoris provided on the wheel circuit board. The wheel encoder ringis connected to the wheel

3 FIG. 3 FIG. 12 12 12 20 20 22 12 22 1 22 2 22 3 22 4 22 1 22 2 22 3 22 4 22 a a a a a a a a a a a a a a a a schematically represents a top view of the AGV. In, the AGVis at standstill. As mentioned, the AGVof this example comprises four wheel unitsand each wheel unitcomprises a wheel. The AGVof this example thus comprises a first wheel-, a second wheel-, a third wheel-and a fourth wheel-. One, several or all of the first wheel-, the second wheel-, the third wheel-and the fourth wheel-may also be referred to with reference numeral “” .

3 FIG. 22 96 24 1 48 96 a a a a. indicates that each wheelhas a heading direction. The X1/Y1-plane of the local coordinate system-may coincide with a plane comprising the wheel axesand the heading directions

22 34 22 22 48 88 22 96 a a a a a a Each wheelmay for example be position controlled by the control system. When each wheelis positioned controlled, a position control loop may be used where a measured position of each wheelaround its respective wheel axis, e.g., as determined based on signals from the respective wheel sensor device, is fed back and compared with a respective target position. A gain of the position control loop may for example be set relatively high such that the compliance of the wheelsin the respective heading directionsis relatively small.

3 FIG. 3 FIG. 22 22 22 24 1 a a a In, the wheelsadopts one example of a wheel configuration by virtue of the respective steering positions adopted by the wheels. In this example, all wheelsare parallel, here parallel with the X1-direction of the local coordinate system-. The wheel configuration inis a valid wheel configuration.

3 FIG. 3 FIG. 98 18 98 98 18 16 98 98 18 18 a a a a a further shows one example of an application forceapplied to the support structure. The application forceconstitutes one example of an application load according to the present disclosure. The application forcemay for example be a force applied on the support structureby the user. The wheel configuration inis not optimal for handling the application force. When the application forceis applied to the support structure, there is a risk that the support structurewill move away from its stationary position.

4 FIG. 4 FIG. 4 FIG. 12 22 22 100 12 a a a a a schematically represents a top view of the AGV. In, the wheelsadopt a further example of a wheel configuration where all wheelsare positioned at respective steering positions in accordance with an instant center of rotation, ICR. Also in, the AGVis at standstill.

22 100 22 24 1 22 a a a a In order to position the wheelswith respect to the ICR, the positions of the wheelsin the local coordinate system-must be known. These positions of the wheelsmay be determined in various ways known to the skilled person, including by measurements.

4 FIG. 3 FIG. 98 22 18 98 a a a Also this wheel configuration is a valid wheel configuration. However, the wheel configuration inprovides a much higher resistance against the application forcethan the wheel configuration in. In order to position the wheelsin a wheel configuration that provides an optimal, or near optimal stiffness of the support structurewith respect to the application force, the following method may be performed.

102 18 34 102 18 102 24 1 a a a A support pointin relation to the support structureis provided in the control system. The support pointis a point in which optimal stiffness of the support structurewill be provided. The support pointmay for example be defined in the X1/Y1-plane of the local coordinate system-.

102 16 102 16 102 44 44 34 a a a The support pointmay be selected arbitrarily. For example, the usermay select the support point. To this end, the usermay provide a selection of the support pointvia the programming device. The selection may then be communicated from the programming deviceto the control system.

102 102 18 22 102 18 22 a a a a a. 4 FIG. Alternatively, the support pointmay be predetermined or set automatically by the AGV control program. The support pointmay for example be predetermined to be horizontally aligned with a geometrical center point of the support structureor a geometrical center point of the wheels. In, the support pointis horizontally aligned with both a geometrical center point of the support structureand a geometrical center point of the wheels

98 18 34 98 24 1 98 18 98 34 a a a a The application forcein relation to the support structureis then provided in the control system. To this end, the application forcemay for example be characterized by a vector in the X1/Y1-plane of the local coordinate system-. The application forcemay be a force acting or estimated to act on the support structure. The application forcemay be provided in the control systemin various ways.

98 16 16 98 44 44 34 a a According to one example, the application forcemay be selected by the user. To this end, the usermay provide a selection of the application forcevia the programming device. The selection may then be communicated from the programming deviceto the control system.

98 98 18 a a According to a further example, the application forcemay be determined based on the AGV control program, prior to execution of the AGV control program. In this case, the application forceis a force estimated to act on the support structurein the future when the AGV control program is executed.

98 26 18 34 20 22 18 102 98 a a a a a. For the above two examples, the application forcemay be associated with a particular task in the AGV control program, such as a task performed by the manipulatorwhen the support structureis at standstill. Thus, when the AGV control program is executed and this particular task is performed, the control systemcan control the wheel unitssuch that the wheelsadopt a wheel configuration that provides an optimal stiffness of the support structurewith respect to the support pointand the application force

98 40 42 70 88 98 18 12 98 102 98 26 18 26 16 18 a a a a a a According to a further example, the application forcemay be determined based on signals from the one or more torque sensors, the one or more force sensors, the one or more of the steering sensor devices, and/or the one or more of the wheel sensor devices. In this case, the application forceis actually applied to the support structureand the AGVcan react to the application forceby adopting a wheel configuration providing a high stiffness in the support point. Moreover, in this case, the application forcemay for example be a force originating from movements of the manipulatorrelative to the support structure, a force originating from the manipulatorcontacting an external object, and/or a force from an external part, such as the user, acting on the support structure.

18 98 98 34 104 106 a a a a. For any load comprising a force acting on the support structure, there exists a point where this load can be represented by a pure force. In line with this, once the application forcehas been provided, the application forceis represented in the control systemby a remote forceacting at a remote point

4 FIG. 4 FIG. 98 18 102 104 106 106 102 108 110 102 106 108 98 48 96 102 106 a a a a a a a a a a a a a a a a In the example in, the application forceacting on the support structureprovides the same torque on the support pointin the horizontal plane as the remote forceacting at the remote point. The remote pointis thus horizontally offset from the support pointand acts in a horizontal remote directiontransverse to an offset linebetween the support pointand the remote point. In the example in, the remote directionis also the direction in which the application forceacts. The wheel axes, the heading directions, the support point, and the remote pointhere lie in a common horizontal plane.

34 22 100 106 34 48 22 106 98 18 102 18 98 14 26 26 a a a a a a a a a In this example, the control systemthen controls all wheelsto adopt respective steering positions such that the ICRcoincides with the remote point. To this end, the control systemmay employ inverse kinematics to determine the respective steering positions. In this wheel configuration, the wheel axisof each wheelpasses through the remote point. This provides a wheel configuration that very efficiently resists the application forceand provides an optimal stiffness of the support structurewith respect to the support point. Thus, the support structurecan more efficiently resist the application forcewithout being caused to move relative to the ground surface. As a consequence, the productivity of the manipulatorcan be increased and the manipulatorcan perform extra challenging manipulation tasks.

12 12 22 2020259830 1 a a a The AGVmay not comprise any dedicated brakes to brake the AGV. Instead, the braking at standstill can be performed by various wheel configurations as described herein. In case the application load comprises only a torque, the wheelsmay be positioned in an X-shape as taught in WOA.

5 FIG. 4 FIG. 5 FIG. 5 FIG. 12 22 1 22 4 100 22 106 22 2 22 3 96 100 22 22 1 22 4 106 102 a a a a a a a a a a a a a a a. schematically represents a top view of the AGV. Mainly differences with respect towill be described. In, the first and fourth wheels-and-are positioned at respective steering positions such that the ICRof these wheelscoincides with the remote point. The second and third wheels-and-on the other hand, are positioned transverse to their ICR orientation, i.e., such that their heading directionsintersect the ICR. The wheel configuration provided by the wheelsinis invalid. The wheel couple comprising the first and fourth wheels-and-spans the widest angle with respect to the remote pointand is therefore the couple that contributes to providing the highest stiffness in the support point

12 98 22 2 22 3 98 22 2 22 3 12 22 2 106 22 2 22 3 22 106 106 22 2 22 3 22 1 22 4 a a a a a a a a a a a a a a a a a a a 5 FIG. Also in this example, the AGVwill exhibit a stiff behavior with respect to the application force. However, the positioning of the second and third wheels-and-provide increased stiffness in case the direction of the application forceshould vary. The second and third wheels-and-thus provide redundancy to the braking of the AGV. In, the second wheel-is most distant from the remote point. Moreover, the second and third wheels-and-are intermediate wheelsas seen from the remote point. That is, as seen from the remote point, the second and third wheels-and-lie between the first and fourth wheels-and the-.

6 FIG. 4 5 FIGS.and 6 FIG. 12 22 1 22 3 22 4 100 22 106 22 2 96 100 22 6 22 2 106 22 2 22 1 22 3 106 12 98 22 2 98 a a a a a a a a a a a a a a a a a a a a a schematically represents a top view of the AGV. Mainly differences with respect towill be described. In, the first, third and fourth wheels-,-and-are positioned at respective steering positions such that the ICRof these wheelscoincides with the remote point. In this example, only the second wheel-is positioned transverse to its ICR orientation, i.e., such that its heading directionintersects the ICR. Also the wheel configuration provided by the wheelsin FIG.is invalid. The second wheel-is most distanced from the remote point. The second wheel-is also an intermediate wheel with respect to the first and third wheels-and-as seen from the remote point. Also in this example, the AGVwill exhibit a stiff behavior with respect to the application force. Moreover, the positioning of the second wheel-provides increased stiffness in case the direction of the application forceshould vary.

7 FIG. 7 FIG. 12 98 18 98 98 102 98 102 98 104 106 102 108 108 102 106 108 112 102 106 98 102 106 22 22 a b b b a b a b b b a b b a b b a b b a b a a schematically represents a top view of the AGVand an application forceacting on the support structure. The application forceis a further example of an application load according to the present disclosure.shows a special case when the application forceacts along a line passing through the support point. The application forcedoes therefore not cause any torque at the support point. When the application forceis represented by remote force, acting at a remote pointhorizontally offset from the support pointand acting in a horizontal remote direction, the remote directionwill also pass through the support point. In this case, the remote pointmay be positioned anywhere along the remote direction, as shown with arrow. As the distance between the support pointand the remote pointincreases, the stiffness will increase, but the resistance against variations in the direction of the application forcewill be decreased, and vice versa. In these cases, the distance between the support pointand the remote pointmay for example be preset to a distance larger than a smallest distance between two of the wheelsand smaller than a largest distance between two of the wheels, such as to an average distance of these two distances.

22 100 22 106 12 98 a b a b a b. 7 FIG. In any case, each wheelis positioned at a respective steering position such that an ICRof these wheelscoincides with the remote point. This provides the wheel configuration shown in, which is a valid wheel configuration. Also in this example, the AGVwill exhibit a stiff behavior with respect to the application force

8 FIG. 1 FIG. 2 FIG. 12 10 12 12 20 12 22 1 22 2 b b b a b a a schematically represents a top view of an AGVaccording to a further example. The systeminmay alternatively comprise the AGV. The AGVof this example comprises two wheel unitsof the type shown in. The AGVthus comprises a first wheel-and a second wheel-.

12 22 1 22 2 22 1 22 2 22 22 96 48 50 b b b b b b b b b b. The AGVof this example further comprises a first wheel-and a second wheel-, here exemplified as swivel casters. A swivel caster is one example of a non-driven wheel. One or both wheels-and-may also be referred to with reference numeral “”. Although being non-drivable, each wheelof this example comprises a heading directionand is rotatable around a wheel axisand around a steering axis

8 FIG. 8 FIG. 98 114 98 114 98 26 114 32 26 32 18 c c c further shows an application forceand a torque. The application forceand the torquecollectively constitute a further example of an application load according to the present disclosure. The application forceis here exemplified as a force acting on the manipulator. The torqueis here exemplified as a reaction torque acting on the first linkof the manipulatordue to a rotation of the first linkrelative to the support structurein the clockwise direction in.

8 FIG. 102 102 32 18 32 b b shows a further example of a support point. The support pointof this example is centered with respect to the first link, here horizontally offset from a geometrical center point of the support structure. Thus, optimal stiffness will be provided in the first link.

102 34 16 34 98 114 18 34 16 40 42 70 88 b c In accordance with the method the support pointis provided in the control system, e.g., selected by the useror by the control system. The application load comprising the application forceand the torquein relation to the support structureis then provided in the control system, e.g., by a selection from the user, by a determination based on the AGV control program prior to execution of the AGV control program, or based on calculations of signals from the one or more torque sensors, the one or more force sensors, the one or more of the steering sensor devices, and/or the one or more of the wheel sensor devices.

104 106 102 108 110 102 106 104 102 98 114 104 98 c c c c c b c c c c c c. 8 FIG. Furthermore, the application load is represented by a remote forceacting at a remote pointhorizontally offset from the support point, and acting in a horizontal remote directiontransverse to an offset linebetween the support pointand the remote point. As can be gathered from, the remote forceprovides the same torque around the support pointas the application forceand the torquein combination. A magnitude of the remote forceis thus larger than a magnitude of the application force

22 100 22 106 32 22 22 22 a c a c b a b 8 FIG. All wheelsare then controlled to be positioned at a respective steering position such that an ICRof these wheelscoincides with the remote point. Optimal stiffness is thus provided at the center of the first link. Since the wheelsare not steerable, these wheels are positioned at random steering positions. In, the wheelsandprovide a further example of a wheel configuration, which is an invalid wheel configuration.

8 FIG. 8 FIG. 104 116 22 1 116 22 2 116 116 48 96 52 12 22 c a a b a a b a a b a As illustrated in, the remote forceis in equilibrium with a first side forceof the first wheel-and a second side forceof the second wheel-. The first and second side forcesandact only in parallel with the respective wheel axisand only transverse to the respective heading directions. Consequently, there will not be any torque applied on the drive motorsas a result of the application load. For the case inwhere the AGVonly comprises two steerable wheels, the method according to the present disclosure is particularly advantageous.

9 FIG. 12 12 12 12 18 20 20 20 20 22 22 48 48 20 20 54 22 50 a b a b a b a b a b a b a a a a. is a flowchart outlining general steps of a method of controlling an automated guided vehicle;, AGV. The AGV;comprises a support structureand at least three wheel units;, each wheel unit;comprising a wheel;rotatable around a horizontal wheel axis;. For at least two of the wheel units, the wheel unitcomprises a steering motorarranged to drive the wheelaround a vertical steering axis

10 102 102 18 12 18 98 98 14 104 104 106 106 102 102 108 108 110 110 102 102 106 106 20 54 16 22 100 100 22 106 106 a b a c a c a c a b a c a c a b a c a a a c a a c. The method comprises providing Sa support point;in relation to the support structure. The method further comprises providing San application load in relation to the support structure, the application load comprising an application force;. The method further comprises representing Sthe application load by a remote force;acting at a remote point;horizontally offset from the support point;, and acting in a horizontal remote direction;transverse to an offset line;between the support point;and the remote point;. The method further comprises for the at least two of the wheel unitscomprising a steering motor, positioning Seach wheelin a steering position such that an instant center of rotation;, ICR, of each wheelsubstantially coincides with the remote point;

20 20 54 22 50 20 54 18 22 20 96 22 108 108 a a a a a a a a a a c. For at least three of the wheel units, the wheel unitmay comprise a steering motorarranged to drive the wheelaround a vertical steering axis. In these cases, the method may further comprise for at least one of the wheel unitscomprising a steering motor, positioning Sthe wheelof the wheel unitin a steering position such that a heading directionof the wheelis substantially transverse to the remote direction;

10 102 102 20 16 44 102 102 a b a b. The provision Sof the support point;may comprise receiving S, from a uservia a programming device, a selection of the support point;

12 22 16 44 The provision Sof the application load may comprise receiving S, from a uservia a programming device, a selection of the application load.

12 24 12 12 40 42 70 88 12 12 a b a b The provision Sof the application load may comprise determining S, by the AGV;using one or more sensors,,,of the AGV;, the application load.

26 12 12 12 28 a b The method may further comprise providing San AGV control program comprising at least one movement instruction for the AGV;. In these cases, the provision Sof the application load may comprise determining Sthe application load based on the AGV control program.

While the present disclosure has been described with reference to exemplary embodiments, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimensions of the parts may be varied as needed. Accordingly, it is intended that the present invention may be limited only by the scope of the claims appended hereto.

In the context of the present disclosure, the steering positions adopted by the respective wheels are said to form a wheel configuration. The wheel configuration according to the method enables an increased stiffness of the support structure with respect to the application load. Since the application load is represented by the remote force acting in the remote direction, the remote direction may be said to be a prioritized direction in which the support structure has an optimally high, or near optimally high, stiffness. The method thus provides a wheel configuration that is adapted to the application load.

Due to the increased stiffness of the support structure provided by the method, the performance of the AGV is improved. The method ensures that any known application load comprising an application force translates to pure side-to-side forces, i.e., in the respective directions of the wheel axes, of the wheels positioned in the respective steering positions to provide the ICR. The positioning of the wheels in the respective steering positions in accordance with the ICR provides a kinematic locking of the wheels and hence a braking of the AGV.

Each wheel is configured to support the support structure on a horizontal ground surface, such as a floor. With stiffness of the support structure is meant the ability of the support structure to resist loads acting horizontally on the support structure without the support structure being caused to move horizontally relative to the ground surface.

The wheel configuration provided by the method may not provide the highest stiffness for an application force acting in any direction. However, for an application force acting in the remote direction, the wheel configuration will provide an optimal, or near optimal, stiffness.

With two or more wheels adopting steering positions to provide an ICR is meant that the wheel axes of these wheels intersect the ICR. For two non-parallel wheels, an ICR will always be provided. For two parallel wheels, the ICR will be infinitely far away from the AGV.

One, several or all of the at least two wheel units comprising a steering motor may also comprise a drive motor arranged to drive the wheel around the wheel axis. In these cases, the positioning of these wheels such that the ICR coincides with the remote point will ensure that the application load does not generate any torque, or any significant torque, on such drive motors. With the ICR substantially coinciding with the remote point may be meant that a maximum distance between the ICR and the remote point is less than 10%, such as less than 5% of a maximum distance between the remote point and one of the wheels.

The AGV may optionally comprise a manipulator. The manipulator may be a robot arm programmable in three or more axes, such as in six or seven axes. The manipulator may be supported on the support structure and movable relative to the support structure. When the AGV comprising the manipulator is at standstill, the support structure is in a stationary position, but the manipulator may move relative to the support structure. The AGV may for example be an autonomous mobile robot, AMR, or an autonomous mobile manipulator robot, AMMR, comprising the manipulator.

Particularly in cases where the AGV comprises the manipulator, the increased stiffness of the support structure provided by the method increases the productivity of the AGV. The increased stiffness of the support structure provided by the method enables the manipulator to perform more advanced tasks, enables the manipulator to perform tasks at higher speeds, enables a reduced or eliminated need for recalibrating the AGV, and enables interactions or more advanced interactions with external objects.

When the manipulator performs a first task that generates a first application load, the wheels of at least two wheel units comprising a steering motor may be positioned in a first wheel configuration in accordance with the method. When the manipulator performs a second task that generates a second application load, different from the first application load, the wheels of at least two wheel units comprising a steering motor may be positioned in a second wheel configuration, different from the first wheel configuration, in accordance with the method. In this way, a time series of different wheel configurations may be provided to provide an optimal stiffness for each task performed by the manipulator. This implies that the support structure may remain at standstill while the manipulator performs several tasks, but at least two of the wheels may rotate around their respective steering axis after completion of each task to provide optimal stiffness for the next task.

The support structure may be a platform. The method according to the first aspect may be performed when the support structure is at standstill.

The method may provide the highest stiffness in the support point. The support point may be selected arbitrarily. The support point may be predefined, may be selected by a control system of the AGV or may be selected by a human user. In any case, the support point may be provided in the control system, either directly or indirectly based on a user input.

The application load may be a load acting or estimated to act on the support structure. Correspondingly, the application force may be a force acting or estimated to act on the support structure. In addition to the application force, the application load may comprise a torque. The torque may be a torque acting or estimated to act on the support structure. In any case, characteristics of the application load, such as one or more vectors thereof in a horizontal plane, may be provided by the control system or online. The representation of the application force by the remote force may be performed by the control system or online.

The steering positions of the at least two wheel units comprising a steering motor may be calculated by inverse kinematics, for example based on a position of the support point, a position of the remote point and a position of the respective wheel unit in a local coordinate system fixed with respect to the support structure. Such calculations may be made by the control system or online. The positioning of the wheels in the respective steering position may be controlled by the control system.

The wheel configuration adopted by the wheels in the method may be either a valid or an invalid wheel configuration. Invalid wheel configurations include all configurations of the wheels except valid configurations. Valid wheel configurations include only an orientation of all the wheels in parallel and an orientation of all the wheels to provide an ICR.

Two, several or all the wheel units may comprise a steering motor arranged to drive the wheel around a vertical steering axis. The method may comprise for all of the wheel units comprising a steering motor, positioning each wheel in a steering position such that an instant center of rotation, ICR, of each wheel substantially coincides with, or coincides with, the remote point. In addition to the at least two steerable wheels, the AGV may comprise one or more non-driven wheels, such as swivel casters or other passive wheels.

The wordings “application load” and “application force” are selected since the application load comprises the application force and since the application force may differ from the remote force representing the application load. The application load, the application force and the remote force may alternatively be referred to as a primary load, a primary force and a secondary force, respectively.

For at least three of the wheel units, the wheel unit may comprise a steering motor arranged to drive the wheel around a vertical steering axis. In these cases, the method may further comprise for at least one of the wheel units comprising a steering motor, positioning the wheel of the wheel unit in a steering position such that a heading direction of the wheel is substantially transverse to, or transverse to, the remote direction. Thus, in cases where more than two steerable wheel units are available, at least one of the wheels may be positioned in this manner. In this way, an increased robustness against variations of a direction of the application force is provided.

The at least one of the wheel units comprising a steering motor may be an intermediate wheel unit as seen from the remote point. Thus, the two wheels creating the widest span towards the remote point may be oriented such that these wheels provide an ICR coinciding with the remote point, while a third intermediate wheel is positioned such that its heading direction is substantially transverse to, or transverse to, the remote direction. Alternatively, or in addition, the at least one of the wheel units comprising a steering motor may be a wheel unit most distant from the remote point.

The provision of the support point may comprise receiving, from a user via a programming device, a selection of the support point. The provision of the application load may comprise receiving, from a user via a programming device, a selection of the application load. The programming device may for example be a teach pendant unit, TPU. The one or more selections by the user may be communicated wirelessly or via a control cable to the control system of the AGV.

The provision of the application load may comprise determining, by the AGV using one or more sensors of the AGV, the application load. The application load may thus for example originate from execution of an AGV control program. In this case, the application load is a load acting on the AGV. Examples of such loads comprise loads originating from the AGV interacting with its environment, e.g., physically contacting an object, and loads originating from movements of a manipulator of the AGV relative to the support structure. In any case, such application loads can be determined by the one or more sensors of the AGV.

The method may further comprise providing an AGV control program comprising at least one movement instruction for the AGV. In these cases, the provision of the application load may comprise determining the application load based on the AGV control program. The application load may originate from the AGV control program as such, e.g., prior to execution of the AGV control program. In this case, the application load is a load estimated to act on the support structure when the AGV control program is executed.

The application load may however comprise a force or a torque that does not necessarily originate from the AGV control program or from an execution of the AGV control program, such as a force or a torque originating from a human pushing the AGV and which can be sensed by the one or more sensors of the AGV.

According to a second aspect, there is provided an automated guided vehicle, AGV, the AGV comprising a support structure; at least three wheel units, each wheel unit comprising a wheel rotatable around a horizontal wheel axis, wherein for at least two of the wheel units, the wheel unit comprises a steering motor arranged to drive the wheel around a vertical steering axis; and a control system comprising at least one data processing device and at least one memory having at least one computer program stored thereon, the at least one computer program comprising program code which, when executed by the at least one data processing device, causes the at least one data processing device to provide a support point in relation to the support structure; provide an application load in relation to the support structure, the application load comprising an application force; represent the application load by a remote force acting at a remote point horizontally offset from the support point, and acting in a horizontal remote direction transverse to an offset line between the support point and the remote point; and for the at least two of the wheel units comprising a steering motor, command positioning of each wheel in a steering position such that an instant center of rotation, ICR, of each wheel substantially coincides with, or coincides with, the remote point. The AGV of the second aspect may be of any type described in connection with the first aspect, and vice versa.

For at least three of the wheel units, the wheel unit may comprise a steering motor arranged to drive the wheel around a vertical steering axis. In these cases, the at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to, for at least one of the wheel units comprising a steering motor, command positioning of the wheel of the wheel unit in a steering position such that a heading direction of the wheel is transverse to the remote direction.

The at least one of the wheel units comprising a steering motor may be an intermediate wheel unit as seen from the remote point.

The at least one of the wheel units comprising a steering motor may be a wheel unit most distant from the remote point.

The provision of the support point may comprise receiving, from a user via a programming device, a selection of the support point.

The provision of the application load may comprise receiving, from a user via a programming device, a selection of the application load.

The AGV may comprise one or more sensors. In these cases, the provision of the application load may comprise determining, by the control system and based on data from the one or more sensors, the application load.

The at least one computer program may comprise program code which, when executed by the at least one data processing device, causes the at least one data processing device to provide an AGV control program comprising at least one movement instruction for the AGV. In these cases, the provision of the application load may comprise determining the application load based on the AGV control program.

According to a third aspect, there is provided a system comprising the AGV according to the second aspect and a programming device configured to be in signal communication with the control system.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

The use of the terms “a” and “an” and “the” and “at least one” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “at least one” followed by a list of one or more items (for example, “at least one of A and B”) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.